1. Field of the Invention
The present invention relates to a head-mounted device. More particularly, the present invention relates to a head-mounted display, mounted on a viewer's head, to display a video image in front of the viewer, and relates to a structure for mounting the device on a viewer's head.
2. Description of the Related Art
In recent years, a head-mounted display which is mounted on a viewer's head is developed. This head-mounted display enlarges a video image displayed on a video display device such as a liquid crystal display and displays the enlarged image in front of the viewer, thereby enabling observation of a large screen video image.
Japanese Patent Laid-Open No. 11-174988 discloses a video display as shown in FIG. 6. In this display, a pair of left and right LCDs 3 as two-dimensional video display devices to display video images corresponding to a viewer's left and right eyes are provided inside an exterior frame 2 of a display main body 1. Further, a pair of backlights 4 to illuminate the LCDs 3 are provided in the rear of the respective LCDs 3, and a pair of prisms 5 respectively to enlarge and guide video images from the LCDs 3 are provided below the LCDs 3. Video images displayed on the LCDs 3 are guided in front of a viewer M's eyes E via an optical observation axis L. While the video images pass through the prisms 5, they are enlarged, and projected so as to be visualized in front of the eyes E.
Further, Japanese Patent Laid-Open Nos. Hei 9-304724 and 2002-262196 disclose structures for mounting a video display as described above on a viewer's head (hereinbelow, “a head-mounting structure”). For example, Japanese Patent Laid-Open No. 2002-262196 discloses a structure as shown in FIG. 7. In Japanese Patent Laid-Open Nos. Hei 9-304724 and 2002-262196, the structure has side frames corresponding to left and right positions of a viewer's head, provided with an occipital pad to be in contact with the viewer's occipital region. The structure presses the display on the viewer's head. The side frames are provided with an adjustment mechanism for fore and aft adjustment of the occipital pad. The video display is fixed on the viewer's head by adjusting the occipital pad in accordance with the size of the viewer's head.
However, in the head-mounting structures disclosed in Japanese Patent Laid-Open Nos. Hei 9-304724 and 2002-262196, the side frames connected to the occipital pad horizontally extend from the same height of the viewer's eye position. Accordingly, the occipital pad is brought into contact with the occipital region of viewer's head in a position on the higher side of the occipital region. Upon use of this structure to fasten the upper part of the viewer's head, the viewer feels as if the display easily slips off the head, and cannot obtain a feeling of comfortable fit.
To provide a comfortable fit to the viewer, as disclosed in Japanese Patent Laid-Open No. 2005-27867, when a portion below the viewer's head—the so-called “hollow of the neck (medulla)”—is pressed, the device can be stably fixed to the head without discomfort. As a structure pressing the peripheral portion of the viewer's hollow of the neck disclosed in Japanese Patent Laid-Open No. Hei 10-142551, a structure in which an arm including a pad to press against the hollow of the neck is attached to a frame passing over the parietal region of the viewer's head.
However, in Japanese Patent Laid-Open No. Hei 10-142551, as an excessive force is applied to a shaft of the occipital pad, it is necessary to design a rotating shaft connecting the frame passing over the parietal region with the arm as a firm member. Further, regarding the arm, because the distance between the point of application of force and the supporting point is long, the arm is distorted, and the required force pressing against the head cannot be obtained. Further, when the strength of the frame and the arm is increased, the weight of the respective members is also increased, thus providing a poor fit and reducing comfort.